[codex] Make GTM Agent brief-native

[a3fckx]

What changed

• Removed the committed campaigns/memory-store-first-gtm campaign workspace from the plugin repo.
• Added brief-operating-surface.md to make the GTM Agent contract explicit: briefs are current operating truth, recall retrieves evidence, records carry confirmed learning/events, and local files are temporary execution ledgers.
• Updated GTM Agent and campaign setup skills to produce an approved operating profile first, record approved policy to Memory Store, and create local files only for import/export, review queues, or explicit handoff.
• Renamed the old campaign-folder guidance in-place to an execution workspace model and updated README, installation docs, Exa setup docs, and eval fixtures to match.

Why

The previous PR made the Memory Store brief contract stronger, but the committed first-campaign folder made the repo look like one static campaign artifact instead of a reusable GTM engineering system. Briefs should now be the product surface; campaign files should be optional runtime/workspace material.

Validation

• python3 -m json.tool plugins/gtm-agent/evals/memory-contract-checks.json >/dev/null
• python3 -m json.tool plugins/gtm-agent/evals/skill-routing-cases.json >/dev/null
• python3 plugins/gtm-agent/scripts/validate_skill_surface.py
• python3 plugins/gtm-agent/skills/campaign-setup/scripts/test_render_gtm_plan_template.py
• git diff --check
• git diff --cached --check
• node /Users/a3fckx/.codex/plugins/cache/openai-curated/plugin-eval/63976030/scripts/plugin-eval.js analyze plugins/gtm-agent --format markdown

Notes

Plugin Eval still reports GTM Agent as 72/C because the overall deferred reference surface is heavy (deferred_cost_tokens around 44.5k). This PR reduces repo artifact bloat by 1,518 net lines, but it does not attempt the larger reference-budget refactor.

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[stage-review]

Ready to review this PR? Stage has broken it down into 8 individual chapters for you:

	Title
1	Update marketplace branding and repository paths
2	Standardize Memory Store brief tool names
3	Establish brief-native GTM operating model
4	Transition GTM Plan to Operating Profile
5	Remove static campaign artifacts
6	Enhance GTM Agent skill context and routing
7	Integrate briefs into Memory Store skills
8	Add comprehensive operating and reproduction guides

_{Chapters generated by Stage for commit 681fc02 on May 13, 2026 5:01am UTC.}